RU2454651C1 - Method for remote determination of thickness of snow cover in avalanche sites - Google Patents

Abstract

FIELD: physics.

SUBSTANCE: method for remote determination of thickness of snow cover in avalanche sites using a laser range-finder is based on comparing measurements of distance from the point of installation of the control and measuring apparatus (laser range-finder) in the valley to control points in the zone of avalanche origin relative a reference point, carried out in two phases: summer season (without snow cover); winter season (with snow cover), taking into account the probing angle. The disclosed method does not require use of expensive aviation equipment. The control and measuring apparatus (laser range-finder) is installed at any easily accessible point in the valley. Distances calculated based on the measurements do not depend on the place where the measuring apparatus is installed.

EFFECT: possibility of obtaining full and timely information on snow thickness in zones of avalanche origin, no risk on the life of people conducting measurement and satisfaction of practical requirements of avalanche stations.

3 cl, 4 dwg

Description

The present invention relates to the field of meteorology and glaciology, and in particular to methods for remotely determining the thickness of snow in the mountains, and can be used to predict avalanche hazard.

There are various methods for remotely determining the thickness of the snow cover in the mountains.

In the Russian technology of avalanche protection to determine the thickness of snow in the centers of avalanche gathering, the use of snow gauges installed in the summer / 1 / is provided.

However, the use of snow gauges to determine the thickness of snow in the centers of avalanche collection is ineffective due to drifts, as well as frequent damage when fired by avalanche shells.

Currently, to obtain information about the state of the snow cover, remote sensing hardware is used that operates in different ranges of the electromagnetic frequency spectrum (visible, microwave, infrared and radar) / 2 /.

Moreover, in most cases, using remote observation tools, as applied to measuring the thickness of the snow cover, only some arbitrarily distinguishable thickness intervals are determined, which is not always a sufficient information parameter for solving practical problems.

In addition, the methods used do not fully satisfy the conditions of snow avalanche stations (SLS) and avalanche units, because they have a number of disadvantages. Their use is associated either with large labor costs, or gives only an approximate idea of the thickness of the snow layer, or the fundamental impossibility of using this method in the conditions of individual SLS. For forecasting avalanche-hazardous situations, snow-avalanche stations and anti-avalanche teams of Roshydromet need prompt and accurate information about the thickness of snow in avalanche gatherings.

The closest in technical essence to the claimed object is a method for remotely determining the thickness of the snow cover in avalanche sites using a laser location, including two consecutive surveys of the terrain, with the first survey taking place in the period preceding the establishment of snow cover (summer measurements), and the second and the following - in the presence of snow cover (winter measurements). The objective of these surveys is, accordingly, obtaining high-precision digital models of the relief of the earth's surface and the surface of the snow cover / 3 /.

To remotely determine the thickness of the snow cover in avalanche centers, it is necessary to use laser location and materials for ground and aerial observations. Of great importance is the design of laser shooting routes and the determination of a sufficient density of laser reflection points per unit area of land and snow.

The disadvantages of this method include the high cost of aircraft and the impossibility of its use in snowfalls, which complicates the implementation of the method for the purpose of active exposure.

The technical result expected from the use of the claimed method is the ability to obtain complete and timely information on the thickness of the snow in the zones of avalanche generation, the absence of risk to people's lives during measurements, the practical needs of the SLS and, unlike the prototype, the use of expensive aviation technology.

The technical result is achieved by the fact that in the known method for remote determination of the thickness of the snow cover in avalanche sites using a laser range finder, which includes sequential surveys of the terrain, the first survey being carried out in the period preceding the establishment of snow cover (summer measurements), and the second and subsequent ones at the presence of snow cover (winter measurements), the rapper and the centers of avalanche origin on the mountain slope are preliminarily selected in the valley, the distances from the installation location of the range finder about control points in the zone of avalanche generation, taking into account the sensing angles, and determine the desired thickness of the snow cover by the formula:

where AE is the difference between the measurement results of the distance from the installation site of the control and measuring equipment (laser range finder) in the valley to the control points in the avalanche nucleation zone relative to the reference point made in the summer period (without snow cover) and in winter (if there is snow cover );

β is the sounding angle.

The technical result is also achieved by the fact that the laser rangefinder is installed in any easily accessible place of the valley, from which the zone of the avalanche and reference nucleation is clearly visible. Moreover, the distances calculated on the basis of measurements do not depend on the installation location of the measuring equipment.

The invention is illustrated by figures, which schematically represent the operation of summer and winter measurements.

Figure 1 presents a diagram of summer measurements in the zone of avalanche nucleation (top view), where C is the location of the laser rangefinder; B - reference (isolated object); A, A ′, A ″ - points in the zone of nucleation of avalanches in avalanche center No._; S - direction to the north (or east, or south - for each avalanche source the most convenient option for choosing the reference direction can be used).

The proposed method is implemented as follows.

- Selects a benchmark (pillar, repeater, etc.) (figure 1 - point B).

- A range meter is installed at point C. The point is selected arbitrarily. Her choice is determined by the following requirements:

a) the rapper is clearly visible - point B;

b) there is direct visibility of the main part of the avalanche nucleation zone in the source No._ (points A, A ′, A ″);

c) it is possible to mount a tripod of a laser rangefinder in accordance with the technical data sheet.

- Determines the distance to the benchmark - segment CB.

- The angle α ₀ (azimuth) of the SCB is determined, under which the frame B is visible.

The angle β ₀ to the horizon is determined, at which point B is observed (Fig. 2, which shows a vertical section along the line of sight at the reference point B, where C is the location of the laser range finder; 1 - the laser range finder installed at point C; B is the reference (isolated object); 2 - horizon line; 3 - angle (β ₀ ) between the direction to the benchmark and the horizon; S - direction to the north (or east or south).

- The distance to points A is determined - the AC segment.

- The azimuth (angle SCA) of observation of point A is determined - angle α.

- Determines the angle β to the horizon at which point A.

- The measurements taken are recorded in table 1.

Similar measurements are made for points A ′, A ″, etc.

The second operation. Calculations for summer measurements.

Figure 3 presents a diagram for calculating summer measurements, where M is the point of intersection of a straight line to the north with a line passing through points A and B.

The ICA angle is calculated:

where the angle SCB is the angle between the line connecting points B and A to the north direction. The value of this angle does not depend on the location of the place (point) of the installation of measuring equipment. Its value depends only on the position of points A, A ′, A ″, etc.

By the cosine theorem we find:

We draw the line DC || VA

Find the angle of CBA:

Find the angle SCD:

The result of summer measurements and calculations are the values:

- angle SCD;

- distance VA.

Calculated on the basis of measurements of distances AB, A′B, A ″ B, etc. also independent of the installation location of the measuring equipment.

The measurements taken are recorded in table 2.

Similar procedures are carried out with points A ′, A ″, etc.

The third operation. Measurements and calculations in the winter (if there is a layer of snow in the mountains).

Figure 4 presents the measurement scheme in the presence of snow cover in the avalanche nucleation zone, where C ′ is the installation site of the laser rangefinder during winter measurements; In - a rapper; A, A ′, A ″ - points in the zone of nucleation of avalanches in avalanche center No._; S - direction to the north; E is a point on a segment of the conditional line C′A; DC ′ is a line parallel to the line connecting points A and B.

- A measurement system (theodolite with rangefinder) is installed at point C ′. Point C ′ may coincide with point C, but this is not necessary.

- The angle γ ₀ is determined (the angle between the directions to the north of S and to the reference point B: ∠BC′S).

- Measured distance C′B.

- Determined β ₀₃ - the angle between the horizon and the direction of the benchmark.

- By summer measurements and winter measurements, ∠C′BA is determined.

Since ∠SC′D = ∠SCD,

where ∠SCD is the angle determined by summer measurements.

- According to the formula:

where AB is calculated from summer measurements, AC ′ is determined.

- The angle AC′V is calculated by the formula:

.arising from the relation

.

- At an angle AC′V, a rangefinder is installed and the distance С′Е is measured.

- The angle β ₃ is determined - the angle between the horizon and the direction to point A.

- The thickness of the snow AE without taking into account the sounding angle AE is determined as the difference:

Given the angle of sounding, the value of h is determined by the formula:

where AE is the difference between the measurement results of the distance from the installation site of the control and measuring equipment (laser range finder) in the valley to the control points in the avalanche nucleation zone relative to the reference point made in the summer period (without snow cover) and in winter (if there is snow cover );

β _s - sounding angle.

An example of a specific implementation of the method

As an example of remote determination of snow cover thickness in avalanche centers using a laser range finder, we present the results of measurements at the NSC Terskol located in the village of Terskol, the Elbrus region, KBR, altitude 2200 above sea level, performed in the period July-December 2009.

In accordance with the claimed method, in the summer, a power transmission line reference point and three conventional foci of avalanche generation on the side of the mountain were chosen. The measurement results are shown in table 3.

Table 3 Measurement results No pp CB, m α ₀ , degree β ₀ , degree AC, m α, degree β, hail A′C, m α ′, degree β ′, degree A′C, m α ″, deg β ″, deg one 305 15 ⁰ 06′57 ″ 7 ⁰ 43′40 ″ 5490 99 ⁰ 48′44 ″ 5 ⁰ 21′15 ″ 5485 99 ⁰ 48′39 ″ 5 ⁰ 21′35 ″ 5480 99 ⁰ 48′25 ″ 5 ⁰ 21′55 ″ 2 305 15 ⁰ 06′57 ″ 7 ⁰ 43′40 ″ 1427 92 ⁰ 01′58 ″ 5 ⁰ 53′45 ″ 1425 92 ⁰ 01′12 ″ 5 ⁰ 54′00 ″ 1425 92 ⁰ 01′00 ″ 6 ⁰ 00′00 ″ 3 305 15 ⁰ 06′57 ″ 7 ⁰ 43′40 ″ 395 63 ⁰ 37′58 ″ 8 ⁰ 44′40 ″ 395 63 ⁰ 37′50 ″ 8 ⁰ 52′28 ″ - - -

The generalized results of calculations by formulas 1-4 are shown in table 4.

Measurements and calculations in the winter (if there is a layer of snow in the mountains).

A measurement system (theodolite with rangefinder) is installed at point C ′. In our case, the point C ′ coincides with the point C.

The angle γ _{0 is} determined (the angle between the directions to the east S and to the reference point B: ∠ВС′S). Because the point C ′ coincides with C, then

∠BC′S = ∠BCS = 105 ⁰ 06′57 ″

С′В = СВ = 305 m

Β ₀₃ is determined - the angle between the horizon and the direction to the benchmark.

∠β ₀₃ = 7 ⁰ 43′40 ″

According to summer (first) measurements and winter measurements, ∠С′ВА is determined. Since ∠SC′D = ∠SCD,

∠C′BA = ∠SC′B-∠SCD,

where ∠SCD is the angle determined by summer measurements. In this case, because the point C ′ coincides with C, ∠C′BA = ∠CBA.

As a result, the value of the angle CBA was obtained for the three measurement zones (table 5).

Table 5 The value of the angle CBA No pp CB, m γ ₀ , degree β ₀₃ , degree ∠C′BA, city ∠C′BA ′, city ∠C′BA ″, city one 305 105 ⁰ 06′57 ″ 7 ⁰ 43′40 ″ 92.12105674 92,11953842 92,12051987 2 305 105 ⁰ 06′57 ″ 7 ⁰ 43′40 ″ 90,74277941 90,73795042 90,74129318 3 305 105 ⁰ 06′57 ″ 7 ⁰ 43′40 ″ 81,6652579 81,6671517 -

The distance AC ′ is determined by the formula:

,

where AB is calculated from summer measurements. The calculation results are shown in table 6.

Table 6 Results of calculating the distance from the installation site of the range finder C ′ to the avalanche nucleation zones No pp AC ′ A′C ′ A ″ C ′ one 5490 5485 5480 2 1427 1425 1425 3 395 395 -

The angle AC′V, at which it is necessary to set the range finder, is calculated by the formula:

The calculation results are shown in table 7.

Table 7 The result of calculating the angle at which it is necessary to install a range finder to measure the thickness of the snow cover No pp ∠AC′B, city ∠A′C′B, city ∠A ″ C′B, city one 84.69638894 84,69500001 84.69111111 2 76,91694442 76,90416667 76,90083329 3 48,51694451 48,51472222 -

The distance С′E is measured from the previously measured angles β ₃ , β, β ₀ (the angles between the horizon and the direction to points A, A ′, A ″, respectively) (table 8).

Table 8 The results of measurements of the distance and vertical angles from the installation site of the laser rangefinder to the snow cover in the direction of points A, A ′, A ″ No pp C′E, m β ₃ , degree C′E ′, m β, hail C′E ″, m β ₀ , degree one 5488 5 ⁰ 21′15 ″ 5484 5 ⁰ 21′35 ″ 5480 5 ⁰ 21′55 ″ 2 1425 5 ⁰ 53′45 ″ 1424 5 ⁰ 54′00 ″ 1423 6 ⁰ 00′00 ″ 3 394 8 ⁰ 44′40 ″ 395 8 ⁰ 52′28 ″ - -

Given the sounding angle β, the snow thickness h is defined as:

h = AE cosβ,

where AE = AC′-EC ′ (table 9).

Table 9 The results of calculating the thickness of snow in the measured areas No pp h mm h ′, mm h ″ mm one 1991,273855 995,627874 0 2 1989,42058 994.702817 1989,043791 3 988,376256 0 -

From the above example it follows that, being at a considerable distance from the avalanche source, where access is life-threatening, the decision to close the affected area by an avalanche, as well as to begin the forced descent of snow (avalanche), depends on the amount of snow calculated by formula 10.

Thus, the proposed method can significantly increase the effectiveness of the security services in recreational complexes in the mountains, as well as services of active impact on snow-avalanche processes.

Information sources

1. Chernous P.A., Barashev G.V., Fedorenko Yu.V. Variability of snow characteristics and the formation of avalanches // Ice and Snow, No. 3. RAS. From the "Science", 2010. S. 27-36.

2. Bogorodsky VV, Poznyak V.I., Trepov G.V., Sheremetyev A.N. Measurement of the thickness of annual snow layers in Antarctica by radar sensing / Doklady AN SSSR 1982. Volume 264, No. 4.

3. Boyko ES Using the method of airborne laser location when assessing snow accumulation in mountain conditions // Materials VI int. conf. “Laser scanning and digital aerial photography. Today and tomorrow". M., 2006. S. 29-30 (prototype).

Claims (3)

1. A method for remote determination of the thickness of the snow cover in avalanche centers, including the sequential conduct of two series of measurements (summer and winter) using a laser range finder, characterized in that using a laser range finder measure the distance from its installation in the valley to the control points in the zone of origin avalanches relative to the reference point and the difference between the measurement results (AE), taking into account the sounding angle (β _s ), determine the thickness of the snow cover (h) by the formula:
h = AE · cosβ _s . 2. The method according to claim 1, characterized in that the laser range finder is installed in any easily accessible place of the valley, from which the zone of the emergence of an avalanche and reference point is clearly visible. 3. The method according to claim 1, characterized in that the distances calculated on the basis of measurements depend not on the installation location of the measuring equipment, but on its resolution.

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